It is important that you look at your son's order carefully. One positive is that this type of order is issued by a civil court, which means that your son will not have a criminal record. However, if he violates the order and by doing anything prohibited by the order, he can be arrested for a misdemeanor. This would mean he would have a criminal record if convicted. Hopefully this will not happen.
Even if he does not have a criminal record, the order will remain a public record. Anyone will be able to see this record. A future employer doing a background check will be able to see it. Maryland law does have the "Shield Law" that may protect your son. Your son may file a written request to shield (to remove from public inspection) the court records relating to a Peace Order if:
"The petitioner (the girl) or the respondent (your son) may file a written request to shield (to remove from public inspection) the court records relating to a Protective Order or a Peace Order if: (1) the Petition for a Protective Order or the Petition for a Peace Order is denied or dismissed at the interim, temporary, or final hearing (it sounds like the hearing has already happened); or
(2) the respondent has consented to the entry of a Protective Order or a Peace Order (I am not sure if this happened in your son's case). A request for shielding may not be filed earlier than three (3) years after the denial or dismissal of the Petition or after the consent expires unless the requesting party files a General Waiver and Release form, CC-DC-077, which is a release of all the requesting party's claims for damages relating to this proceeding and any tort claims that may arise out of this proceeding. The court will schedule a hearing on the request to shield, after which a judge will rule on the request."
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